The field of video endoscopy, to which the present invention generally relates, includes medical diagnostic and therapeutic disciplines that utilize endoscopes to penetrate and view otherwise inaccessible body cavities utilizing minimally invasive surgical procedures. Coupling of video imaging cameras (incorporating solid-state imagers) to endoscopes, for image reproduction, has become standard within the field. Endoscopic video cameras (hereinafter referred to as “camera heads”), are most advantageously small and lightweight for ease of use by medical personnel, and typically incorporate either single or multiple solid-state imagers. Some special purpose endoscopes have integrated (built-in) solid-state imagers, which do not facilitate direct viewing of internal body cavities by medical personnel without an accompanying video imaging system and display. To achieve the desired size and weight, camera head and/or integrated endoscope-camera assembly electronics are typically separated physically from the majority of circuitry required to process and output high-quality, color video images.
Typically, endoscopic camera heads are sterilized prior to each use, because camera heads and endoscopes enter the “sterile field” during a surgical procedure. Camera control units (“CCUs”), which contain the majority of the electronic circuitry required to process video images, are typically not sterilized, and are placed on or in carts, or permanently wall-mounted. In known video imaging systems, interconnection is achieved by means of a cable, with usually one cable end permanently fixed to the camera head, while the other cable end is detachably connected to the CCU using a connector. Similar to the camera head itself, it is advantageous that cables be small in diameter and lightweight, but rugged enough to withstand repeated sterilization, accidental gurney wheel “run-over,” and the like.
Known video imaging systems typically include at least one camera head with a fixed cable, and often either a CCU having various input connections or different CCUs for each camera type. The input connections to the CCU are keyed so that specific camera heads can only be connected to a specific one of various inputs or to a particular CCU that corresponds to that particular camera head specifications. Timing signals, video system function command signals, and camera head supply voltages are all generated in the CCU for transmission to the camera head. The advantage to this camera head arrangement is small size, lightweight and easy maneuverability. Disadvantageously, only camera heads requiring timing signals matched to the CCUs timing generator may be utilized with this arrangement. Therefore, new or differing camera heads utilizing different timing signals cannot be utilized.
Another disadvantage of known video imaging systems is that the various camera heads have differing cable structures based upon the camera head parameters. Each camera head typically is matched to its own specifically configured cable.
Existing interconnections between camera heads and CCUs typically comprise dedicated parallel wires to provide greater data carrying capacity. It is meant by “dedicated parallel wires” that each specific signal is transmitted by means of an individual wire, either single for power and control signals or shielded coax for image data, between a camera head and CCU. However, a disadvantage of providing dedicated parallel wires is that typically twenty to thirty separate lines are required to control, energize and receive image data from camera heads, with most signal lines requiring a dedicated connector pin. The more lines required, the greater the diameter, size and corresponding weight of the cable bundle. The larger this bundle becomes, the more likely it is to interfere with medical personnel's use of the video imaging system. Moreover, utilizing dedicated parallel wire type cabling is undesired when additional functionality is required and added to either the camera head or CCU. To accommodate this new functionality, additional wiring must be incorporated in the cable bundle, requiring equipment redesign and subsequent purchase by customers. Also, as video imaging systems develop, CCUs are becoming programmable for compatibility with various types of camera heads, are adding new control features and are processing different types of video signals.
Another aspect of video imaging systems is that undesired image “noise” can be encountered, due to stray electromagnetic signals being induced upon the wires of the cable bundle (commonly referred to as electromagnetic interference, “EMI”), and from signal “cross-talk” within the cable itself. Known video imaging systems utilize analog signals for transmitting video and other signals to or from camera heads and CCUs. These analog signals, especially image data, are very susceptible to EMI from surgical electro-cautery equipment and the like. The use of EMI shielding is prohibitive due to the added cost and subsequent cable size and weight increase. Moreover, the desired endoscopic camera head cable length itself (typically 10 feet or more) tends to induce noise as analog signals are propagated down its length.
Additionally, solid-state imaging devices of higher resolution are becoming available and commercially feasible for use in video imaging systems. As imagers increase in sophistication, greater amounts of image data must be transmitted by means of the interconnection cable between camera heads and CCUs, and thus higher speed data transmission means must be utilized.
What is desired, therefore, is to provide a video imaging system where interconnection of camera heads is not limited to only those camera heads compatible with the timing signals generated in the CCU. Rather, a video imaging system is desired that enables the CCU to process image data and receive control signals from, and to issue command signals to, many types of camera heads, each having differing timing signal requirements.
It is further desired to provide a video imaging system that is resistant to both internal and external electromagnetic interference that does not require utilization of heavy shielding. This advantageously will enable the use of a small diameter, lightweight cable.
It is further desired to provide a video imaging system enabling camera heads and CCUs to take advantage of new features and functions without requiring redesign and/or replacement of the system. Such a configuration would provide the ability to accommodate future video camera system improvements and adaptations as current technology limitations are overcome, without obsolescing initial customer investments in CCUs.
It is further desired to provide a video imaging system that enables the use of a single pair of wires for transmission of control, command and image data transmission from and to the camera head and the camera control unit.